So did the Master Yi changes just essentially nutshot the whole idea of AP Yi? Because it sounds like everything runs though AD with him now.

His alpha strike no longer scales of AP, yes. He still gets "yi-sets" since his ult still reduces his cooldowns on kills/assists and will prolong the ult. You can no longer prep double strikes. His e has been changed to add a true damage active. Also the targeting on alpha strike has changed some as well.

He likely won't be such a monster early on, and you won't have to deal with a deathcap/lichbane Yi gibbing you. But he'll still be a pentakill machine once he's geared, maybe even more so now. He'll be countered pretty hard by armor stacking, but the active on his e will help mitigate that some.